ACTINOMYCETES. 377 



which ultimately form colonies having more or less 

 resemblance to true mycelia. Certain of the threads 

 composing such a mycelium become fruit hyphae, break- 

 ing up into round, glistening, spore-like bodies. As a 

 rule, these spores are devoid of the high resistance to 

 heat exhibited by bacterial spores, and are stainable by 

 the ordinary methods. 



The limits of this group are ill defined and its recog- 

 nized components are not as a whole well understood. 



The longest known and most carefully studied acti- 

 nomycetes are act. bovis, act. madurse, act. farcinicus, 

 and act. Eppingeri, although many other varieties have 

 been encountered in association with important and 

 interesting pathological lesions. 



The fact that certain bacteria, viz., b. tuberculosis, b. 

 mallei, b. diphtheria?, generally regarded as bacteria, 

 are, as a rule, segmented and occasionally show a ten- 

 dency to branch, has led to their being classified at 

 times with the actinomycetes ; on this point, however, 

 there is as yet no consensus of opinion. 



It is interesting to note that the pathological lesions 

 in which actinomycetes have been detected show in many 

 cases certain similarities to true tubercular processes, 

 and in a few instances, save for the absence of tubercle 

 bacteria, as we usually see them, were indistinguishable 

 from tuberculosis. 



More or less imperfectly studied varieties of actino- 

 mycetes have been encountered in abscess of the brain, 

 cerebrospinal meningitis, endocarditis, bronchopneumo- 

 nia, pleuropneumonia, pustular exanthemata, abscess of 

 the lung, bronchiectasis, pulmonary gangrene, necrosis 

 of the vertebra?, subphrenic abscess, noma, pseudotuber- 

 c,ulosis, etc. 



